Regulating transformer for arc welding by alternating current



June 24, 1930. v F. WORTMANN" REGULATING TRANSFORIER FOR ARC WELDING BY ALTERNATING CURRENT Filed Nov. 11, 1925 nun 2&2224 2 I i I v v v 1 d: e

Patented June 24, 1930 UNITED STATES PATENT}, OFFICE,

rnANz won'rmnn, or GENEVA, SWITZERLAND, 'ASSIGNOR r soorE'rE' ANONYME nrzs ATELIEBS or: SECHERON, or GENEVA, SWITZERLAND, A CORPORATION or SWITZERLAND I REGULATING TRANSFORMER FOR ARC WELDING BY ALTERNATING CURRENT Application filed November 11, 1925, Serial No. 68,468, and in Germany December 23, 1924.

The invention refers to a regulating transformer for arc-welding by alternating current.

It is characterized by the fact that the arrangement of the series of connections of the transformer is such that by reducing the welding current the no-load tension is thereby positively increased automatically.

In the drawing Figure 1 is a diagrammatic plan illustrating one of the possible constructions of a transformer made in accordance with my invention.

F ig.'2 is a diagrammatic plan illustrating the relationship between the current and voltage in the secondary circuit under different conditions.

Fig. 3 is a diagrammatic plan similar to Fig. 1, but showing another form of the invention, and

Fi 4 is also a diagrammatic plan similar to Figs. 1 and 3, but showing still another form of the invention.

Referring to Fig. 1 the magnetic frame ofthe transformer comprises two longitudinal limbs a, b and three transverse branches 0, (Z, 6., A part f of the primary winding 7 is fitted to the limb a and is connecte at one end In with the source of electricity (not shown), at the other end,

with a? contact 1. Another part, of this primary winding is arrangedon t e limb b and is divided into a plurality of sections h, z', One end. of section II. is connected to a contact 1, the common ends of sections it and e to a contact 2, the common ends of sections 2' and j to a contact 3 and the yet free remaining end of section j to a contact 4. A contact arm n maybe brought in touch with the several contacts 1 to 4 and is permanently in connection with the other pole of the source of electricity. The secondary winding op, feeding the arc is for one part fitted to the limb b and hr the other part to the transverse branch 0, in order that the dispersion may be increased. The part f of the primary winding therefore has a greater dispersion with reference to the secondary winding, than thepart The working of the described trans ormer is as follows:

If only the part f of the primary winding fg which lies on the limb 0; works, then the induction of the magnetic circuit and therefore the no-load tension of the trans former are great. The leakage of the primary and secondary windings fg, op on the contrary is greatest with this arrangement, so that in this case the current arising from a short circuit of the secondary winding, or the current circulating when welding is smallest. If the part 9 of the primary winding f-g lying on limb b is also thrown in, then the induction of the magnetic circuit is diminished, but the leakage is also diminished, so that in the case of ashort circuit of the secondary winding 0- or in welding, a stronger current is produced. The proportion of the leakage of both parts 7, g is under such conditions so adjusted that by reducing the weldin current the no-load tension is necessari y ingreased positively and automatically there- This is of great importance for arcwelding by alternating current: In known apparatus for arc-welding by direct current or by alternating current, the regulation is such, that, when a current of low strength, is used, the no-load tension'is also diminished or it remains constant. This has no great importance in the case of direct current 7 machines, for, according to the characteristic curve shown in Fig. 2, the are tension A changes in a scarcely noticeable manner, for short arcs and strength of current from about 60 amps. and the extent of the no-load tension needs be considered only for the lighting of the arc and the greatest possible length of arc. Very great, on the other hand, is the effect of the no-load tension on the stability of the arc in the case of welding by alternating current. In such case, the current is interrupted 100 times per second with a current having 50 alternations. In introducing every half wave, the tension must in the first place rise to a certain value (the lighting tension B) in order that the current might set again. The height of the lighting tension B 18 dependent to an extraordinarily great extent, on the current strength and increases very considerably with a small current strength, as is shown by Fig. 2. For this reason known alternating current welding apparatus have a noload tension of to 90 volts, whereas for a current strength of 180 amps. for instance, 60 volts are amply sufficient. By fixing the welding current at 100 amps. the'no-load tension must amount to volts approximatively in order to ensure a steady arc. In the case of welding with currents of less than 100 amps. the no-load tension must be still higher. The disadvantages of a high no-load tension are important, for the primary current in welding increases proportionally to the no-load tension; this demands rather large quantities of copper for the windings and the leads and also brings about a deterioration in the efficiency factor. These disadvantages are overcome in the use of the transformer herein shown and described.

In accordance with Fig. 3 the part 0 of the secondary winding is provided with contacts 11, 12, 13, 14, which may be connected by a movable contact (not shown) to leads 9', s, t, it permanently connected to the ends of sections o, w, :0, 3 of part 0. The are q is connected tothose ends of parts 0, p which still remain free.

If the movable contact is brought in touch with contact 11, then the no-load tension is greatest and the produced current smallest; when the movable contact lies on contact 14, the no-load tension is smallest and the welding current greatest, as, at each time a section on the limb Z) is cut ofi', a greater section on branch 0 is thrown in. On reducing the welding current the no-ioad tension necessarily increased automatically. the latest constructional form (Fig. 4) Isa-5h parts 0, p of the secondary winding c are arranged on limb I). Part is pro- 'll'. i l with contacts 21, 22, 23, 24, 25, 26 with whicn. the movable lead 2, leading to the are 5, may be connected. When connecting the arc q to 20 and 26 the no-load tension is smallest and the welding current greatest, when connecting it to 20 and 21 the no-load tension is greatest, the welding current smallest. An adjustment to the desired r0- portion between no-load tension and strength of current is obtained in the manufracture of the apparatusby alteration of the air-gaps 18, 19 between the transverse branch d and the longitudinal limbs (1,6.

In this manner the no-load tension of the regulating transformer is adjusted to the reouirements of the are, so that the greatest stability of said arc is obtained with a small- I est quantity of copper.

What I claims 1s: e

1. In an alternating current weldin transformer for simultaneous regulation 0% voltage and current intensity, a core, prixed mary and secondary windings on the said core, one of the said windings having a plurality of groups of turns, and means for switching 1n and out said groups of turns whereby a number of turns are eliminated from one winding and a greater number of turns are inserted into another winding so that there is included in the circuit with each added group a sufiiciently greater number of turns to effect an increase in the no load tension and a corresponding reduction of the welding current, and vice versa.

2. In an alternating current welding transformer for simultaneous regulation of voltage and current intensity, a core, a primary winding on the said core, a secondary winding on the said core, one of the said windings being divided into a main group of turns and a pluralit of auxiliary groups of turns, and means or switching in and out said auxiliary groups of turns whereby a number of turns are eliminated from one winding and a greater number of turns are inserted into another winding so that there is included in the circuit with each additional group a sufficiently greater number of turns to efl'ect an increase in the no load tension and a corresponding reduction of the welding current, and vice versa.

3. In an alternating current welding transformer for simultaneous regulation of voltage and current intensity, a core, a primary winding thereon, a secondary winding also on the said core, the secondarywinding being divided into a main group of turns and a plurality of groups of auxiliary turns, and means for switching in and out the said auxiliary groups of turns of the secondary winding whereby a number of turns are eliminated from one winding and a greater number of turns are inserted into another winding so that there is included in the circuit with each added grou a sufficiently greater number of turns to e ect an increase in the no load tension and a corresponding reduction of the welding current, and vice versa.

In testimony whereof I afiix my signature.

FRANZ WGRTMA'NN. 

